Geared actuator



May 22,1951 A. J. wETTELs 2,554,436

' GEARED AcruA'roR A.

Filed May 9, 194e @fw INVENTOR. l l

i f BY Patented May 22, 1951 GEARED ACTUATOR Albert J. Wettels, Minneapolis, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application May 9, 1946, Serial No. 668,529

13 Claims.

The present invention relates to positive stop means for a geared motor driven actuator.

Mechanical stop means have long been used to limit the rotation of the main or output shaft of motor driven actuators and have performed satisfactorily when used with small and relatively low speed motors. However, when the prior art stop means are applied to the more powerful actuators driven by high speed motors, through speed reducing power transmission means such as a gear train excessive stresses result with consequent damage to the gear train and other parts of the device. The present invention overcomes these difficulties by using cam me-ans driven by the gear train near its output end to actuate stop means effective against abutment means rotated by the said gear train near its input or motor driven end. By stopping the gear train at a point where the torque is low, stresses are kept low and damage is prevented.

It is therefore a principal object of this invention to provide improved stop means for a motor driven geared actuator.

It is also an object to provide positive stop means for a geared actuator which is actuated by the gear train near its output end but is effective near the driven end of the said gear train.

It is a further object to provide improved means for positively stopping rotation of a motor means without subjecting the means to eX- cessive stresses.

It is an additional object to provide stop means effective to stop the gear train of a geared actuator and to provide torque limiting clutch means to minimize the stress in the said stop means.

It is also an object to provide geared motor means with improved means for positively limiting rotation in at least one direction and to provide friction means for preventing rotation when the motor is deenergized in either direction.

It is a further object to provide geared motor driven actuator means with positive stop means so arranged that the eifect of the inertia forces of the gear train and the motor are minimized.

It is also an object to provide stop means for a geared motor driven actuator which is easy to manufacture and dependable in service.

It is a further object to provide stop means for a gear train which is readily adapted to varying arrangements of the said gear train.

These and other objects will become apparent upon a study of the following specication and drawings wherein:

Figure 1 is a side elevation of the present motor driven actuator., with parts in section.

Figure 2 is a schematic representation of the gear train and stop'means as viewed from the line 2-2 of Figure 1.

Figure 3 is an elevation view of the stop cam and the friction clutch shown in Figure 1.v

Figure 4 is an elevation view of the actuating cams of Figure 1,'slightly rotated.

Figure 5 is a schematic. representation of a modified stop means.

The present actuator, best shown in Figure 1, is espectially designed for use in aircraft for actuating valves, dampers, flaps and the like requiring limited travel and -in consequence is made as light as possible consistent with dependability and its power demands. Actuator I 0 includes a motorhousing II secured to gear housing I2 by means not shown. A partition I3 is properly located and held in place by rabbet means near the junction line of housings II and I2, the said partition I3 separating the motor compartment from the gear compartment.

Motor I4, located within housing I I, is pref` erably a two phase induction motor and includes field coils I 5 secured to housing I I. An armature or rotor I6, preferably with herringbone or skewed slots, vis attached to shaft I'I and located within the influence of the field coils I5. A brake drum I8, also mounted on `shaft I'I has conical braking surfaces and is shown in engagement with a brake ring comprising a ring of suitable fric' tion material, such as a cork-synthetic rubber composition or the like, held between two metal rings and secured as at 20 to partition I3. Brake drum 'I8 is normally held in engagement with braking means I9 and armature or rotor I6 is slightly to the left of its magnetic-center due to the thrust exerted by spring 22 on shaft I'I through plate 2|, the spring being held in place by a cap means 23 which is suitably secured to housing II. Spring 22 exerts a force such that the armature I6 and disk I8 is normally rheld# against rotation when one phase of the motor is not energized but wherein, upon energization of both phases of the motor, the tendencyof armature I5 to gain its magnetic center is sufficient to overcome spring 22, drum I8 is moved out of engagement with braking means I9 and motor I4 operates a speed reducing power transmission means which herein is gear-train 25 through pinion 26 carried on the left end of shaft I 1.

Pinion 26 at the high speed, low torque end of gear train 25 engages gear 21 on shaft- 28,

which gear is rotatable relative to shaft 28 but;

is normally prevented from turning relative to the said shaft by torque limiting clutch means comprising plate 29 secured to shaft 28, fric- In addition to the above mechanism,V 'pinion 36 is also connected to shaft'28zand engages gear 31 carried on shaft 38. Pinion-'39.on the said shaft 38 engages gear 40 carried by shaft 4|, the right end of shaft 4| being cutaway to render the drawing less confusing. A pinion 42 secured to shaft 4| engages gear 43 mounted on shaft 44. A pinion 45 secured to shaft 44 engages gear 45`fwh'ich drives main `or outputshaft`41 to which issecured n'operating arm '48," the said operating arm 48 being preferably prevented from rotating elative'tofshaft 41"by"splin`es or the like, not shown. Any conventional'fastening means such as"nutlllY may be used to prevent'removal of arm 48 Ffromuthe saidfshaftl Shaft 41 is`` thus the main utputshaft r`th`e low speed high torque endvof the present actuator device., In addition to Ipinion 45 andlgearn43, actuating cams 5| and garelalsomounted'on shaft 44. Camsl 5| and 52 nhave,cylindrical vsurfacesv/'ith the exception ot recesses 53 and 55 respectively, vthe .,said recesses being bounded at'v their. 4adjacent ends byLdrop offvfaces 5,4 andj', respectively. In the present-instanca dropeff.faces 54A and 56are apprximately 309.,angularddegrees apart inthei'rfunctional relation.

.A.. aime-f crossed., rivotallyfmounted lever meansl andzar .lncatedfbetweenams 32.-,33 email-521 lLever. V I. is;i;11..a1ieriment.-With Cram Stand cam 32, whereaslever 32.is in alignment withscam 52 and cam 433; Lever 6| has an abutting-portion 3. andr a yfollower. A portion 64, while` -lever |52 ahas -ang abutting portion 65, and -a followerffportion"66.5 These crossed levers are p ivotallyfmounted on astub shaft 61 attached to partition |3,; the-.said shaft being aligned with and located Abetweenshafts' 2B and 44.- Follower portions 64- and :66 .of levers ,6|V and62, respectively, are urgedv againstf-cams-`| and 52, respectively,vbyspring means 68. f The purpose and function'of Ythese leversl will be made more clear inthe description of thef operation of the present mechanism.

-It'was previously noted'that drop oif faces 54 and 56 of'camsr'5l and 52, respectively, were located 300 angular degrees apart. It should be furtherY noted'that" this angularity has worked wellinv the present `commercial embodiment of this apparatus wherein the gear train is proportioned as follows: 12 teeth l'on pinion 26, 60 teeth orf'gear 21, 14 teethpon pinion` 36, 70 teeth on gear`3'1,114 teethfon pinion 39, 72 teeth on gear 40, I5' teeth" on pinion'42, 63 teeth onu gear 43, 15 teeth dri pinion'45, and '50"teeth ongear 46. Calcula,- tinwill reveal that the overall reduction of the presentr'gearktrain iswl8`00l to l and the reduction netween'shafts gaand 4415103 to 1,Y In addition. the'redution between shafts 44 andoutput shaft 41-i s 3,1/3 to 1. As will be'lat'er described, with a 31/,3'` toll ratio between shafts 44 vand output shaft 41;', szhaft41 WillV rotaten 90 degrees while shaft 44.

rotatesOQ, degrees., In this present example, motor |4 operatesat about 10,000 R. P. M. and

output shaft 41 can rotate through its 90 degree travel in about 2.6 seconds.

While the actual stopping of the present gear train takes place at one step removed from the motor, and the actuation of the stop means is one step removed from the output shaft, it is obvious that the actuation can be from the output shaft itself and-the stopping can be on-the motor shaft itself, if desired. In the present instance, it was found more convenient and entirely satisfactory to locate the stop means as shown. It Will be noted that levers 6| and 62 are crossed because cams .5V-52' and 32-33 rotate in opposite directions. If' these cams rotated in the same directionthen a different arrangement of the stop vlevers would be called for.

i cams VVbeing carried on shaft 28. These cams have abutment faces 34-and 35 as in the preceding example and itis furtherfassumed thatshaft 2-8 is` one step removed from th'e motor driving means. actuating means will .be rotated in the same. directionras shaftj28, it maylbe'assumed `that 'actue ating cams5| andV 52 are secured .tooutputshaft 41 andutherefore rotate. in the 'same direction as shaft 28. Acuating cams'. 5| and 52 Aare generally similar to the aforementioned actuatingicams excepting that Athey :have 'somewhatllonger recess portions` .53. Tand-:555i andvidrop loif` faces 54' and 56 arermuchclosertogether so thatv each. of leversf1| .and .12':.can beactua'ted vvith-'90Y degrees rotationfof v"shaft 4.1.. Lever means`1| and'12. have abutment rfaces13 and 14 and@ follower portions 15 .-andff1, respectively. Levers 1| and 12 are pivoted on a stub shaft 6.1. located `in alignmentfwith:butspaced from the a plane defined byshafts 28"and41, as shown in Figure 5. Follower portions 15 and 16 are held in engagement with their respective cams 5| y and 52fby a tension spring means 11.

Motor |4 is connected vto .controlling electrical circuits through an ANconnector 19, the circuits normally being controlled by an velectronic amplier such as that disclosedin the copending application of Albert P. Upton, Serial No. 437,561,`

filed April 3, 1942, now Patent No. 2,423,534.

.To better illustrate the present invention, the` operation of the present mechanism will now be described.

Operation In Figure 1, device I0 is shown in its partiallyy e' deenergeized condition and, by referring to Figure 2, it Will be noted that main or output shaft 41` has been rotated to one of its 'extreme positions. Assuming that pinion 26 was rotating clockwise when shaft 41 was moved to its eXtreme, then shaft 41 would Abe driven in a counterclockwise v direction, hence it is now inrits extremercounterclockwise position. Further, since the motor is partially deenergized, armature orY rotor I6V is pushed vto the left of`its magnetic center by spring .22 and brake drum I8 is" in engagement with friction ring I9.

However, sov that the :shaft carrying the 4I flitnw be assumed that motqrmeas'l'l'ajis energized vfor rotationin-a direction Aopposite to' its previousenerg'izatin, so that`pinion"26` will 'rotate' counterclockwise," it will be noted'that Aare rotatedcunterclockwise hence follower por-A tions 64 'and 66 will 'both ride on the cylindrical surfaces of the',A said cams'until recess `53"'paisses under follower means 64 and permits abutment portion 63 tdmove against its stop cam 32 for engagement with abutment surfac'e34 of the said cam.

' In the meantime, however, should the motor be partially deenergized because of the control' ling action of its amplier, or the like, armature I6 would then be' moved to the left as before noted with brake drum I8 engaging brake ring I9 and preventing 'further rotation. This will prevent rotation of output leverI 48 because the braking effort preventing rotation of pinion 26 is multiplied 1800 times by the gear train. With the present arrangement, a relatively small brakingforce is thus able to hold a considerable load on the outputl shaft. i However, should the motor continue rotating in its previous direction with pinion 26 'rotating'` counterclockwise, this rotation will lcontinue as before noted until follower portion 64 drops off face 54 into recess' 53 of cam 5I. vAbutment portion 63 is then in a position to engage, vand does engage, abutment face 34 of the cam 32, as before noted. Now, if motor means I4 is rotating at 10,000 R. P. M., as previously noted, shaft 28' which carries'the stop cam's 32 and 33 will be r0- tating at 2,000 R. P. M. This shaftl will be abruptly stopped in the manner described hence it will appear that the inertia of the rapidly revolving motorv may cause a considerable shock. However, because motor means I4 transmits its effort'to shaft 28 through gear 21 and friction disk 30, shaft 28 can be abruptly stopped and the shock is minimized by slipping of gear 21 relative to plate 29 due to the aforementioned clutch means. Therefore, the lforces to be handled by levers 6I and 62 in stopping the gear train are the limiting torque permitted by the clutch means and the inertia of the gear train itself. However, since the speed at shaft 23 has been re-v duced to 2,000 R. P. M. and the speed at shaft 38 is further reduced to '400 R. P. M., with addition-l al reductions in speed through the rest of the gear train, the inertia forces of the gear train itself are not large and are easily handled by the present stop means. While 300 degrees of rotation are required of shaft 44 before `follower 64 can drop into recess 53 of cam 5I, only 90 degrees of rotation takes place at shaft 41 duev to the aforementioned 31/3 to 1 gear reduction between shafts 44 and 41. Thus, when abutment portion 63 engages abutment face 34 of cam 32 and brings the gear train to a stop, arm 48 and shaft 41 will be in their eXtreme clockwise position and 90 degrees removed from the aforementioned extreme position.

The operation of the mechanism lin Figure is vquite similar to that just described. In the -po- Yr sition,'shown, shaft 14' may be assumed lto 'have otatedto its extreme 'counterclockwise direction so thatfollower portion 15 of'lever 1I fell oif drop off portion 56 of cam 52 and thus permitted portion 13 of lever 1IA to engage stop face-35 of cam 33. This prevents vfurther rotation of shaft 28 in a counterclockwise direction, as will beobvious, If it now -be considered that the motor means which drives this apparatus yis oppositely energized and rotates shaft 28 in a clockwise di'- rection, it will be noted that lever 1I is cammed outwardly by stop cam 33 thus forcing follower portion 15 away from cam 52. While it might appear that face 5B of cam 52' would engage leverv 1I and prevent clockwise rotation of shafts 41 and 28, it is noted that the very considerable gear reduction between shafts 28 and 41 permits considerablerotation of shaft 28 with only slight movement at shaft'41. In practice, this gives no difficulty. Rotation being started in a clockwise direction, it will continue until the motor is par-F tially deenergized as in the previous example, or until recess 53 of cam 5I passes under follower portion 16 of lever 12 therebyl permitting abutment portion 14 of lever 12 to be pulled into engagement with cam 32 so that lit can engage abutment face 34Vof the said cam and prevent further clockwise rotation. This will then prevent fur` ther clockwise rotation of shaft 41 due to the aforementioned gear train. Because shaft 41 in this'example isthe output shaft, it is noted that the drop off faces 56 andv 54 are so located that onlyy the required Vangular rotation of shaft 41 is' permitted, in this case degrees. This will `,be seen vby inspecting Figure k'wherein it will be noted that when shaft 41 rotates approximately 90 degrees, drop olf face 54' will then pass under follower portion 16 of lever 12. It should be noted that the limitingrotation described in these eX- amples is illustrative only, 90 degrees being chosen because the operating arms of the present actu# ators are commonly limited to 90 degrees rotation.- Obviously, Vby shifting cams 5I and 52', or 5I and 52', relative to each other, any desired angular rotation may be had in accordance with the present invention.

A study of the present disclosure will suggest many substitutions and equivalents hence it is emphasized that the present disclosure is to be considered as illustrative only and with the scope of the present invention being determined by the appended claims.

Iclaim: l. In an actuating device, motor means including an armature, an output shaft for said device, a torque increasing gear train including a plurality of gears connected between said armature and said output shaft so that said shaft has a high output torque compared to said armature, means for braking said armature when the said motor means is deenergized, oppositely arranged ratchet'tooth means connected to said gear train for low torque and relatively high speed operation thereby, cam means driven by a portion of the gear train which operates at relativelyvhigh torque and low speed, friction clutch means arranged in said gear train between said armature and said ratchet tooth means, a pair of crossed pivoted levers each having a follower portion and an abutting portion and arranged in straddling relation to said cam means and said ratchet tooth means, said cam means including circular portions and recess portions, and means urging the said follower portions against said cam means, said lever means being proportioned and larranseasothat the abutting. portiegscfsed levers clear said .ratchet teeth means Wreaths Seid ich lower portions are, engaging the simular Portions of ksaid cam means but wherein an abutting portion engages a ratchet tooth means and prevents further rotation in one direction of said gear train when the respective follower means engages a recessv portion of Vsaid c arn means, said friction clutch means preventing undue shock on the gear train when the ratchet tooth means is suddenly Stopped- 2. In an actuatingdevice, motor means including an armature, an output shaft for said device, aspeed reducing gear train including a plurality of pairs of gears connected between said armature and said output shaft so that said shaft is driven at a relatively low speed by said armature, oppositely arranged ratchet tooth means con.- nected to said gear train for relatively high speed rotation thereby, cam means connected to said gear train for relatively low speed rotation thereby, a pair of lever means arranged in straddling relation to said cam means and ratchet tooth means, said cam means including actuating portions for operating one or the other of said lever means, and means for holding said lever means in engagement with said cam means, each of said lever means also including a portion for engaging one of said ratchet tooth means when said lever means is actuated by one of said cam operating portions but which is normally held out of Vengagement with said ratchet tooth means by said cam means, the engagement of said lever means with said ratchet tooth means limiting operation of said gear train and thus limiting rotation of said output shaft.

3. In an actuating device, motor means including an armature, an output shaft, a gear train comprising a plurality of pairs of gears for driving said output shaft at a speed less than that of said armature, oppositely arranged ratchet means driven by said gear train at a relatively high speed, cam means driven by saidgear train at a relatively low speed, said camv means having dwell portions and a pair of depressed portions, spring means, crossed lever means having inwardly directed follower means urged against opposite sides of said cam means by said spring means, and said lever means having ratchet engaging portions held out of engagement with said ratchet means when said follower means engages the dwell portions of the cam means but wherein one of said engaging portions engages vsaid ratchet means and prevents further rotation in one direction of said ratchet means and gear train when its respective follower means engages a depressed portion of said cam means.

4. In an actuating device, motor means including an armature, an output shaft for said device, a plurality of' speedrreducing gears connecting said armature to said output shaft so that said shaft will be driven with relatively high'torque and low speed as compared to said armature, means including oppositely arranged axially displaced ratchet teeth connected to one of said gears for relatively high speed rotation thereby, cam means having cylindrical portions and angularly related axially displaced operating portions, a pair of levers pivotally mounted in straddling relation to said ratchet means and said cam means, each of said levers having a cam follower portion and a ratchet tooth abutting portion, said levers being arranged so that each lever is in rotative alignment with a ratchet tooth and a @am operating portion, and means for maintainfgageable with said brake means.

8, ing bother said ,follower portions engagement with said cam: means said abutting" persoas clearing said ratchet teeth means when said follower portions are engaging said cylindricai Apor-l tions and one o r the other of said abutting p0rtions engaging its aligned ratchet tooth means when its respective follower is displaced byan operating portion rof said cam means to llimit rota? tion of said gears and said output shaft.

5. In an actuating device, motor means including a rotor, said device including a main shaft, speed reducing power transmission meansconf necting said rotor to said main shaft, lever 6911.-. trolling and actuatingA means included in said power transmission' means and `located near one extremity thereof, means including an abutment included in said power transmission means and located near the opposite extremity thereof, and lever means controlled by said lever controlling and actuating means and including a stop por-v tion engageable with said abutment means to stop said power transmission means and said main shaft when said lever is operated byisad lever actuating means.

V6. In an actuating device, motor means including a rotor, a main shaft for said device, speed reducing power transmission means connecting said rotor to said main shaft, said power transmission means including torque limiting means, means preventing operation of said power transe mission means when said motor means is deenerf, gized, means for controlling and actuating stop, means connected in positive rotative relation with said main shaft and rotatable at a relatively low Speed by said power transmission means,-mcans including an abutment driven at relatively high speed by said power transmission means, and stop means controlled by said controlling and actuating means and including a portion en: gageable with said abutment means to stopV said power transmission means and said main` shaft when the said stop means is actuated.

7. In an actuating device, motor means including a rotor, a main shaft for said device, speed reducing power transmission means connecting ysaid rotor to said main shaft, positive brake means included in said power transmission means` for relatively high speed rotation thereby, control means includedin said power transmission means for relatively low speed operation thereby, and mechanical means arranged for actuation by said control means for engaging said Apositive brake means for stopping operation of said power transmission means.

8. In a motor driven device, said motor includ: ing a rotor, an output shaft, speed reducing power transmission means connecting said rotor to said shaft for driving said shaft Iat a relativelylow speed, positive brake means connected to said power transmission means for relatively high speed rotation thereby, control means connected to said power transmission means for relatively low speed operation thereby, said control means being positively related to said output shaft, and mechanical means controlled by said control means and capable of engaging said brakej means,

said mechanical means comprising a `vpair of pivoted lever means having portions engageable with said control means and other portions en- 9. In a motor driven device, said motor including a rotor, an output shaft, speed reducing power transmission means connecting said rotorto said shaft for driving said shaft :at a relatively low speed, positive brake means. .Connectedtesgil power transmission means for relatively high speed rotation thereby, control means connected to said power transmission means for relatively low speed operation thereby, said control means being positively related. to said output shaft, and mechanical means controlled by said control means and capable of engaging said brake means, said mechanical means comprising a pair of pivoted lever means arranged in straddling relation to said control means and said brake means, said levers having inwardly directed follower portions bearing against said control means and having end portions engageable with said brake means, said levers being pivoted about an axis arranged between said brake means and said control means.

l0. In a motor driven device, said motor in cluding a rotor, :an output shaft, speed reducing power transmission means connecting said rotor to said shaft for driving said shaft at a relatively low speed, positive brake means having an axis connected to said power transmission means for relatively high speed rotation thereby, control means having an axis connected to said power transmission means for relatively low speed operation thereby, said control means being positively related to said output shaft, and mechanical means controlled by said control means, capable of engaging said brake means, said mechanical means comprising a pair of pivoted lever means arranged in straddling relation to said control means and said brake means, said levers having inwardly directed follower portions beare ing against said control means and having end portions engageable with said brake means, said levers being pivoted about an axis located on a continuation of a plane defined by the axes of said control means and said brake means.

11. In brake means for the gear train of lan actuator, positive stop brake means mounted on and rotatably driven by an input end of the gea-r train, cam means mounted on and driven by an output end oi the said gear train, and pivoted lever means having a. portion for following said cam means and having another portion arranged to engage said positive stop means when properly actuated by said cam means.

2. In brake means for the gear train of an actuator, positive stop brake means mounted on and rotatably driven by a low torque end of the gear train, cam means mounted on and dri-ven by a high torque end of the said gear train, and lever means having a portion arranged to engage said brake means for stopping rotation thereof and having `another portion for bearing against said cam means and normally preventing engagement oi the irst named portion.

13. In stop means for a :speed reducinggear train, said gear train having a high speed end and a low speed end, the said low speed end including an output shaft, rotatable ratchet tooth means mounted on said gear train near its high speed end, cam means mounted on the said output shaft, and pivoted lever means controlled by said cam means and arranged to engage said ratchet tooth means to prevent rotation thereof.

ALBERT J. WETTELS.

REFERENCES CITED The following references are of record in the file or this patent:

UNITED STATES PATENTS Number Name Date 2,285,414 Collins June 9, 1942 2,378,941 May June 26, 1945 

